<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="../../vue.js"></script>
</head>

<body>
  <div id="app">
    <button v-on:click="decrement(1)">-</button>
    <h1>{{count}}</h1>
    <button @click="increment($event,1)">+</button>
  </div>

  <script>

    var vm = new Vue({
      el: "#app",
      data: {
        count: 0
      },
      methods: {
        increment(e, num) {
          this.count += num;
          console.log(e.target)
        },
        decrement(num) {
          this.count -= num;
        }
      }
    })

  </script>

</body>

</html>